In this paper, the modeling and analysis of single bi-layer Si-QD solar cell is addressed. The modeling of solar cell is done in MATLAB. The photo currents are calculated for various Si-QD diameters like 2.5, 3, 3.5 and 4 nm and SiO2 barrier layer thicknesses like 2.5, 2 and 1.5 nm. It has been observed that with the Si-QD diameter, the photo-current increases. On the other hand, photo-current varies conversely with barrier layer thickness due low carrier tunneling probability through barrier.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3100

Bohra, S.S.

Panchal, A.K.

English

Electronic Sumy State University Institutional Repository

JOURNAL OF NANO- AND ELECTRONIC PHYSICS  ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ Vol. 5 No 2, 02006(3pp) (2013)  Том 5 № 2, 02006(3cc) (2013)  2077-6772/2013/5(2)02006(3)  02006-1   2013 Sumy State University Modeling of Si-QD Solar Cell in MATLAB  S.S. Bohra1, A.K. Panchal2  1  Electrical Engg. Dept. ,Sarvajanik College of Engg. and Tech., Athwalines, Surat, 390 001 Gujarat, India 2  Elect. Engg. Dept., SVNIT, Ichchhanath, Surat, 395 007 Gujarat, India  (Received 15 February 2013; published online 04 May 2013)  In this paper, the modeling and analysis of single bi-layer Si-QD solar cell is addressed. The modeling of solar cell is done in MATLAB. The photo currents are calculated for various Si-QD diameters like 2.5, 3, 3.5 and 4 nm and SiO2 barrier layer thicknesses like 2.5, 2 and 1.5 nm. It has been observed that with the Si-QD diameter, the photo-current increases. On the other hand, photo-current varies conversely with bar-rier layer thickness due low carrier tunneling probability through barrier.  Keywords: Quantum Dot, Si-QD, Barrier layer, Quantum Confinement Effect (QCE), Photo-current.    PACS numbers: 84.60.Jt, 81.16. – c   1.  NTRODUCTION  The  introduction  of  quantum  dots  application  in photovoltaic  devices has drawn  the attention of many researchers. Reducing the cost incurred by silicon (Si) wafer is the major advantage. At the same time develop-ing high efficiency solar cells using single material lim-ited  by  its  band-gap  is  a  difficult  task.  Reducing  the number of steps involved in the fabrication of solar cells is  also  essential  for  cost  cutting.  All  these  challenges have  motivated  researchers  for  3rd  generation  solar cells. Researchers use nano-particles or quantum dots of different  materials  for  enhancing  light  absorption, charge generation, and the efficiency of solar cells. In order to reduce the overall cost of high efficiency solar cells,  researchers  fabricate  quantum  structure  of  di-mension  less  than  10 nm.  The  Si  nano-crystals  or  Si quantum dots (Si-QD) of diameter less than 10 nm show quantum  confinement  effect  (QCE).  The  QCE  allows engineering band-gap of a material with QDs by control-ling  QDs  size  [3].  Indeed,  the  quantum  confinement effect manifests itself by significant modification of elec-tronic band structure of Si nanocrystals when their size is reduced to below the exciton Bohr radius (~4.9 nm) of bulk  Si  crystals.  In  particular,  quantum  confinement effect provokes the increasing of the effective bandgap of Si  nanocrystals.  Moreover,  for  indirect bandgap  semi-conductors, like Si, geometrical confinement of carriers increases  the  overlap of  electron  and  hole  wave  func-tions in momentum space and thus enhances the oscil-lator  strength  and  as  a  consequence  increases  its  ab-sorption coefficient. From this effect, one can expect Si nanocrystals to behave as direct bandgap semiconduc-tors. Though, the momentum conservation rule is only partially broken and Si nanocrystal strongly preserves the  indirect  bandgap  nature  of  bulk  Si  crystals  Si nanostructures are thus the perfect candidates for high-er bandgap materials in all-Si tandem cell approach. Carrier  tunneling  probability  through  dielectric, known as barrier layer increases as its thickness redu-ces  [1].  Based on  this  concept  very  thin  SiC,  SiNx or SiO2 layer in superlattice (SL) can be used in the Si-QD cell. In the present modeling and simulation work, the super lattice with QDs having bandgap in the range of 1.5-2.0 eV  has  been  introduced  as  intrinsic  layer  (i-layer) for absorbing high energy photons [2]. QDs in a-Si layers sandwiched between dielectric layers in a super lattice structure increases its bandgap energy, which in turn should increase VOC [3].    Fig. 1 – Schematic of all- Si Tandem solar cell  Ab initio calculations using density functional theory (DFT)  indicate  that  the  increasing  of  the  optical bandgap of Si nanocrystals (or in other words quantum dots (QDs)) is expected to vary from 1.4 to 2.4 eV for a nanocrystal size of 8-2.5 nm. However, further DFT cal-culations have found that in addition to quantum con-finement effect in small QDs, the matrix has a strong influence of the resulting energy levels. Some  researchers  [4,  5]  have  used  RF  magnetron sputtering to deposit alternating layers of SiO2 and SRO (Si rich oxide formed by co-sputtering Si and SiO2) of thicknesses  down  to  2 nm.  Deposition  of  multilayers, consisting  typically  of  20-50  bi-layers,  is  followed  by anneal in N2 ambient from 1050 to 1150  C, typically for 1 h.  During  annealing,  the  excess  silicon  in  the  SRO layer precipitates to form Si nanocrystals between the stoichiometric oxide layers, as shown in Fig. 2. The  thin  multilayer  structure  ensures  that  the  Si QDs are constrained in diameter by the layer thickness and  a  reasonably  uniform  size  dispersion  is  achieved with variation within about 10 %. Transport properties are expected to depend on the matrix in which the silicon quantum dots are embedded. As  shown  in  [6],  different  matrices  produce  different transport barriers between the Si dot and the matrix, with tunneling probability heavily dependent on the   S.S. BOHRA, A.K. PANCHAL  J. NANO- ELECTRON. PHYS. 5, 02006 (2013)  02006-2   Fig. 2 – Schematic of Si-QD solar cell superlattice in i-layer    Fig. 3 – Bulk band alignment between crystalline silicon and its carbide, nitride and oxide, the band gap increases for quan-tum confined Si dots of 3 nm diameter to 1.73 eV  height of this barrier. Si3N4 and SiC give lower barriers than SiO2 allowing larger dot spacing for a given tun-neling current.  2.  ALGORITHM  The steps involved in modeling of Si-QD solar cell in MATLAB are as shown below:   The  number  of  photons  corresponding  to  wave-length,   from 280 nm to 1200 nm is read from excel file [9];   As shown in Fig. 4 the average Si QD diameter in-creases as the O/Si ratio is decreased from 1.3 to 0.86. The Si QDs are approximately 4 nm in the SiO0.86/SiO2, 3 nm  in  SiO1.0/SiO2  and  2.5 nm  in  SiO1.3/SiO2.  The measured optical absorption of these samples is shown in Fig. 5.    Fig. 5 – Si QD diameter as a function of O/Si ratio in annealed SiOx/SiO2 multilayer films [5, 6]    For  given  range  of  ,  absorption  co-efficient,    is read. The value of   for different dot sizes like 2.5, 3, 4 nm [4] have already been computed beforehand and stored in separate excel worksheet.   Find absorptance and from it find number of photons absorbed in silicon QD layer. As barrier layer of SiO2 is sandwiched between two consecutive layers of Si-QD, carrier tunneling is to be considered to find effective number of carriers tunneled through  barrier  layer.  Hence,  tunneling  probability  is computed  for  given  (E0 – E),  i.e.  from  2 eV,  1.75 eV, 1.65 eV and 1.5 eV to 3.2 eV for QD sizes of 2.5, 3, 3.5 and 4 nm respectively. Some researcher [11] has came up with a simple generalised analytic model describing the size-effective bandgap (EQD) for the lowest energy states for 3D confinement:   2 2223.6 2 eQD bulkqE E smallertermsd d  (1)  Where, Ebulk is the bulk bandgap, ε is the silicon die-lectric constant taken to be 11.7,   is the reduced mass of the electron-hole pair, and d is the nanocrystal diam-eter.    Fig. 6 – Room temperature absorption co-efficient of annealed SiOx / SiO2 multilayer [4], [6]  The  probability  that  a  carrier  will  tunnel  through  a dielectric can be expressed as follows:   022 ( )16 exp 2 tm E ETW   (2)  where, Tt   Tunneling probability, m*   effective mass of electron,  E0   Barrier  height,  E   Energy  of  carrier,    Planck’s constant and W   barrier thickness[4]. From expression (1) it is understood that reducing barrier width or dielectric thickness increases tunneling probability.  The  difference  term  between  conduction band edges of SiO2 layer and Si-QD (E0 – E) can be cal-culated by using expression given below:   2 ,,0 2g SiO g Si QD EEEE   (3)  where, Eg,SiO2   Conduction band edge of Silicon Oxide and Eg,Si-QD   Conduction band edge of Silicon quantum dot  [7].  For  example  by  substituting  the  values Eg,SiO2   9 eV  and  Eg,Si-QD   Eopt,Si-QD   2.6 eV  in  expres-sion  (3),  we  get  E0 – E ≈ 3.2 eV.  As  the  bandgap  of  i-layer  increases,  the  cell’s  VOC  is  expected  to  increase significantly [8-11]:   For the carriers that posses energy higher than bar-rier height of 3.2 eV in case of SiO2, carriers will not tunnel through barrier but simply passes through the barrier  and  generates  electron-hole  pair  (EHP).   MODELING OF SI-QD SOLAR CELL IN MATLAB   J. NANO- ELECTRON. PHYS. 5, 02006 (2013)   02006-3   Photo current for single layer of Si-QD and barrier layer is found by integrating carriers available at the surface of the cell.   J0 is assumed to be 9.6   10 – 9 mA/cm2   VOC  is  found  from  the  standard  expression  given below:   0ln 1 scOCJ nkTVqJ  (4)      3.  RESULTS AND DISCUSSION  As shown in Table 1 modeling of Si-QD solar cell is done  for  single  bilayer  of  SiO2  and  SRO.  In  order  to analyse the dependency of dot diameter on the photo-current, various dot sizes are chosen like 2.5, 3, 3.5 and 4 nm with different barrier layer thicknesses like 1.5, 2, 2.5 nm. It is clear from the results that the short-circuit current Jsc for 2.5 nm dot diameter (EQD   2 eV) is  0.3859 mA/cm2  for  2.5 nm  barrier  layer  thickness, whereas, for 4 nm dot diameter Jsc has been increased to  1.247 mA/cm2  for  1.5 nm  barrier  layer  thickness. Open circuit voltage VOC is varying with dot size and inversely with barrier layer thickness. Table 1 – Description of the special paragraph styles  Thickness SiO2  2.5 nm  2 nm  1.5 nm Dot Size (nm) EQD (eV) Jsc (mA/cm2) Voc (Volt) Jsc (mA/cm2) Voc (Volt) Jsc (mA/cm2) VOC (Volt) 2.5  2  0.3859  0.4525  0.4071  0.4539  0.456  0.4568 3  1.75  0.6266  0.465  0.6579  0.4663  0.7294  0.4689 3.5  1.65  0.8817  0.4738  0.9268  0.4751  1.0288  0.4778 4  1.5  1.055  0.4785  1.1138  0.4799  1.247  0.4828  4.  CONCLUSIONS  In this work the single layer Si-QD solar cell has been modeled and simulated for wavelength 280 nm to 1200 nm. The model has been simulated for various dot sizes like 2.5, 3, 3.5 and 4 nm and various barrier layer thicknesses like 2.5, 2 and 1.5 nm. From the results, it has been concluded that as the dot size increases the QCE  decreases  and  the  optical  band-gap  approached towards bulk Si material i.e. 1.124 eV from 2 eV, 1.75, 1.65 and 1.5 eV for Si-QD sizes of 2.5, 3, 3.5 and 4 nm respectively.  The  Jsc  is  found  to  increase  from 0.3859 mA/cm2 to 1.055 mA/cm2 for 2.5 nm dot size to 4 nm for barrier layer thickness of 2.5 nm. On the other hand, the Jsc also increases with reduction in barrier layer thickness, i.e. from 1.055 mA/cm2 for 2.5 nm thick barrier  layer  to  1.247 mA/cm2  for  1.5  thick  barrier  layer.   REFERENCES  1.  P.S.M. Sze,  Physics  of  Semiconductor  Devices,  2nd  Ed. (John Wiley & Sons Inc.: 2007). 2.  Tae-Wook Kim,  Chang-hee Cho,  Baek-Hyun Kim,  Appl. Phys. Lett. 88, 123102 (2006). 3.  V. Vinciguerra,  G. Franzo,  F. Priolo,  F. Iacona,  J.  Appl. Phys. 87, 8165 (2000). 4.  Gavin Conibeer, Ivan Perez-Wurfl, Xiaojing Hao, Dawei Di, Dong Lin, Nanoscale Res. Lett. 7, 193 (2012). 5.  Gavin Conibeer, et al., Prog. Photovoltaics: Res. Appl. 19, 813 (2011). 6.  X.J. Hao A.P. Podhorodecki, Y.S. Shen, G. Zatryb, J. Misiewicz, M.A. Greenet, Nanotechnology 20, 485703 (2009). 7.  Kavita Surana,  University  of  Grenoble,  France,  Thesis (2011). 8.  Dawei Di,  Heli Xu,  Ivan Perez-Wurfl,  Martin A. Green, Gavin Conibeer, Prog. Photovoltaics: Res. Appl. (2011). 9.  D. Kovalev,  H. Polisski,  G. Koch,  phys.  status  solidi  (b) 215, 871 (1999). 10. Nae-Man Park,  Chel-Jong Choi,  Tae-Yeon Seong,  Seong-Ju Park, Phys. Rev. Lett. 86, 1355 (2001). 11. Pramila Mahala, Sanjay Kumar Behura, A. Ray, J. Nano- Electron. Phys. 3 No1, 979 (2011).   

Chel-Jong Choi, Tae-Yeon Seong, SeongJu Park,

Ivan Perez-Wurfl, Xiaojing Hao,

phys. status solidi (b) 215,

Physics of Semiconductor Devices, 2nd Ed.

Modeling of Si-QD Solar Cell in MATLAB

SocioEconomic Challenges Journal (Sumy State University)

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ 
Vol. 5 No 2, 02006(3pp) (2013) Том 5 № 2, 02006(3cc) (2013) 
 
2077-6772/2013/5(2)02006(3) 02006-1  2013 Sumy State University 
Modeling of Si-QD Solar Cell in MATLAB 
 
S.S. Bohra1, A.K. Panchal2 
 
1 Electrical Engg. Dept. ,Sarvajanik College of Engg. and Tech., Athwalines, Surat, 390 001 Gujarat, India 
2 Elect. Engg. Dept., SVNIT, Ichchhanath, Surat, 395 007 Gujarat, India 
 
(Received 15 February 2013; published online 04 May 2013) 
 
In this paper, the modeling and analysis of single bi-layer Si-QD solar cell is addressed. The modeling 
of solar cell is done in MATLAB. The photo currents are calculated for various Si-QD diameters like 2.5, 3, 
3.5 and 4 nm and SiO2 barrier layer thicknesses like 2.5, 2 and 1.5 nm. It has been observed that with the 
Si-QD diameter, the photo-current increases. On the other hand, photo-current varies conversely with bar-
rier layer thickness due low carrier tunneling probability through barrier. 
 
Keywords: Quantum Dot, Si-QD, Barrier layer, Quantum Confinement Effect (QCE), Photo-current. 
 
 PACS numbers: 84.60.Jt, 81.16. – c 
 
 
1. NTRODUCTION 
 
The introduction of quantum dots application in 
photovoltaic devices has drawn the attention of many 
researchers. Reducing the cost incurred by silicon (Si) 
wafer is the major advantage. At the same time develop-
ing high efficiency solar cells using single material lim-
ited by its band-gap is a difficult task. Reducing the 
number of steps involved in the fabrication of solar cells 
is also essential for cost cutting. All these challenges 
have motivated researchers for 3rd generation solar 
cells. Researchers use nano-particles or quantum dots of 
different materials for enhancing light absorption, 
charge generation, and the efficiency of solar cells. In 
order to reduce the overall cost of high efficiency solar 
cells, researchers fabricate quantum structure of di-
mension less than 10 nm. The Si nano-crystals or Si 
quantum dots (Si-QD) of diameter less than 10 nm show 
quantum confinement effect (QCE). The QCE allows 
engineering band-gap of a material with QDs by control-
ling QDs size [3]. Indeed, the quantum confinement 
effect manifests itself by significant modification of elec-
tronic band structure of Si nanocrystals when their size 
is reduced to below the exciton Bohr radius (~4.9 nm) of 
bulk Si crystals. In particular, quantum confinement 
effect provokes the increasing of the effective bandgap of 
Si nanocrystals. Moreover, for indirect bandgap semi-
conductors, like Si, geometrical confinement of carriers 
increases the overlap of electron and hole wave func-
tions in momentum space and thus enhances the oscil-
lator strength and as a consequence increases its ab-
sorption coefficient. From this effect, one can expect Si 
nanocrystals to behave as direct bandgap semiconduc-
tors. Though, the momentum conservation rule is only 
partially broken and Si nanocrystal strongly preserves 
the indirect bandgap nature of bulk Si crystals Si 
nanostructures are thus the perfect candidates for high-
er bandgap materials in all-Si tandem cell approach. 
Carrier tunneling probability through dielectric, 
known as barrier layer increases as its thickness redu-
ces [1]. Based on this concept very thin SiC, SiNx or 
SiO2 layer in superlattice (SL) can be used in the Si-QD 
cell. In the present modeling and simulation work, the 
super lattice with QDs having bandgap in the range of 
1.5-2.0 eV has been introduced as intrinsic layer (i-
layer) for absorbing high energy photons [2]. QDs in a-Si 
layers sandwiched between dielectric layers in a super 
lattice structure increases its bandgap energy, which in 
turn should increase VOC [3]. 
 
 
 
Fig. 1 – Schematic of all- Si Tandem solar cell 
 
Ab initio calculations using density functional theory 
(DFT) indicate that the increasing of the optical 
bandgap of Si nanocrystals (or in other words quantum 
dots (QDs)) is expected to vary from 1.4 to 2.4 eV for a 
nanocrystal size of 8-2.5 nm. However, further DFT cal-
culations have found that in addition to quantum con-
finement effect in small QDs, the matrix has a strong 
influence of the resulting energy levels. 
Some researchers [4, 5] have used RF magnetron 
sputtering to deposit alternating layers of SiO2 and SRO 
(Si rich oxide formed by co-sputtering Si and SiO2) of 
thicknesses down to 2 nm. Deposition of multilayers, 
consisting typically of 20-50 bi-layers, is followed by 
anneal in N2 ambient from 1050 to 1150 C, typically for 
1 h. During annealing, the excess silicon in the SRO 
layer precipitates to form Si nanocrystals between the 
stoichiometric oxide layers, as shown in Fig. 2. 
The thin multilayer structure ensures that the Si 
QDs are constrained in diameter by the layer thickness 
and a reasonably uniform size dispersion is achieved 
with variation within about 10 %. 
Transport properties are expected to depend on the 
matrix in which the silicon quantum dots are embedded. 
As shown in [6], different matrices produce different 
transport barriers between the Si dot and the matrix, 
with tunneling probability heavily dependent on the  
 S.S. BOHRA, A.K. PANCHAL J. NANO- ELECTRON. PHYS. 5, 02006 (2013) 
 
02006-2 
 
 
Fig. 2 – Schematic of Si-QD solar cell superlattice in i-layer 
 
 
 
Fig. 3 – Bulk band alignment between crystalline silicon and 
its carbide, nitride and oxide, the band gap increases for quan-
tum confined Si dots of 3 nm diameter to 1.73 eV 
 
height of this barrier. Si3N4 and SiC give lower barriers 
than SiO2 allowing larger dot spacing for a given tun-
neling current. 
 
2. ALGORITHM 
 
The steps involved in modeling of Si-QD solar cell in 
MATLAB are as shown below: 
 The number of photons corresponding to wave-
length,  from 280 nm to 1200 nm is read from excel 
file [9]; 
 As shown in Fig. 4 the average Si QD diameter in-
creases as the O/Si ratio is decreased from 1.3 to 0.86. 
The Si QDs are approximately 4 nm in the SiO0.86/SiO2, 
3 nm in SiO1.0/SiO2 and 2.5 nm in SiO1.3/SiO2. The 
measured optical absorption of these samples is shown 
in Fig. 5. 
 
 
 
Fig. 5 – Si QD diameter as a function of O/Si ratio in annealed 
SiOx/SiO2 multilayer films [5, 6] 
 
 For given range of , absorption co-efficient,  is 
read. The value of  for different dot sizes like 2.5, 3, 
4 nm [4] have already been computed beforehand and 
stored in separate excel worksheet. 
 Find absorptance and from it find number of photons 
absorbed in silicon QD layer. 
As barrier layer of SiO2 is sandwiched between two 
consecutive layers of Si-QD, carrier tunneling is to be 
considered to find effective number of carriers tunneled 
through barrier layer. Hence, tunneling probability is 
computed for given (E0 – E), i.e. from 2 eV, 1.75 eV, 
1.65 eV and 1.5 eV to 3.2 eV for QD sizes of 2.5, 3, 3.5 
and 4 nm respectively. Some researcher [11] has came 
up with a simple generalised analytic model describing 
the size-effective bandgap (EQD) for the lowest energy 
states for 3D confinement: 
 
 
2 2 2
2
3.6 2e
QD bulk
q
E E smallerterms
d d
 (1) 
 
Where, Ebulk is the bulk bandgap, ε is the silicon die-
lectric constant taken to be 11.7,  is the reduced mass 
of the electron-hole pair, and d is the nanocrystal diam-
eter. 
 
 
 
Fig. 6 – Room temperature absorption co-efficient of annealed 
SiOx / SiO2 multilayer [4], [6] 
 
The probability that a carrier will tunnel through a 
dielectric can be expressed as follows: 
 
 0
2
2 ( )
16 exp 2t
m E E
T W  (2) 
 
where, Tt  Tunneling probability, m*  effective mass of 
electron, E0  Barrier height, E  Energy of carrier, 
  Planck’s constant and W  barrier thickness[4]. 
From expression (1) it is understood that reducing 
barrier width or dielectric thickness increases tunneling 
probability. The difference term between conduction 
band edges of SiO2 layer and Si-QD (E0 – E) can be cal-
culated by using expression given below: 
 
 2
, ,
0
2
g SiO g Si QDE E
E E  (3) 
 
where, Eg,SiO2  Conduction band edge of Silicon Oxide 
and Eg,Si-QD  Conduction band edge of Silicon quantum 
dot [7]. For example by substituting the values 
Eg,SiO2  9 eV and Eg,Si-QD  Eopt,Si-QD  2.6 eV in expres-
sion (3), we get E0 – E ≈ 3.2 eV. As the bandgap of i-
layer increases, the cell’s VOC is expected to increase 
significantly [8-11]: 
 For the carriers that posses energy higher than bar-
rier height of 3.2 eV in case of SiO2, carriers will not 
tunnel through barrier but simply passes through the 
barrier and generates electron-hole pair (EHP). 
 
 MODELING OF SI-QD SOLAR CELL IN MATLAB  J. NANO- ELECTRON. PHYS. 5, 02006 (2013) 
 
 
02006-3 
 Photo current for single layer of Si-QD and barrier 
layer is found by integrating carriers available at the 
surface of the cell. 
 J0 is assumed to be 9.6  10 – 9 mA/cm2 
 VOC is found from the standard expression given 
below: 
 
 
0
ln 1scOC
JnkT
V
q J
 (4) 
 
 
 
 
 
3. RESULTS AND DISCUSSION 
 
As shown in Table 1 modeling of Si-QD solar cell is 
done for single bilayer of SiO2 and SRO. In order to 
analyse the dependency of dot diameter on the photo-
current, various dot sizes are chosen like 2.5, 3, 3.5 and 
4 nm with different barrier layer thicknesses like 1.5, 
2, 2.5 nm. It is clear from the results that the short-
circuit current Jsc for 2.5 nm dot diameter (EQD  2 eV) 
is 0.3859 mA/cm2 for 2.5 nm barrier layer thickness, 
whereas, for 4 nm dot diameter Jsc has been increased 
to 1.247 mA/cm2 for 1.5 nm barrier layer thickness. 
Open circuit voltage VOC is varying with dot size and 
inversely with barrier layer thickness. 
Table 1 – Description of the special paragraph styles 
 
Thickness SiO2 2.5 nm 2 nm 1.5 nm 
Dot Size 
(nm) 
EQD 
(eV) 
Jsc 
(mA/cm2) 
Voc 
(Volt) 
Jsc 
(mA/cm2) 
Voc 
(Volt) 
Jsc 
(mA/cm2) 
VOC 
(Volt) 
2.5 2 0.3859 0.4525 0.4071 0.4539 0.456 0.4568 
3 1.75 0.6266 0.465 0.6579 0.4663 0.7294 0.4689 
3.5 1.65 0.8817 0.4738 0.9268 0.4751 1.0288 0.4778 
4 1.5 1.055 0.4785 1.1138 0.4799 1.247 0.4828 
 
4. CONCLUSIONS 
 
In this work the single layer Si-QD solar cell has 
been modeled and simulated for wavelength 280 nm to 
1200 nm. The model has been simulated for various dot 
sizes like 2.5, 3, 3.5 and 4 nm and various barrier layer 
thicknesses like 2.5, 2 and 1.5 nm. From the results, it 
has been concluded that as the dot size increases the 
QCE decreases and the optical band-gap approached 
towards bulk Si material i.e. 1.124 eV from 2 eV, 1.75, 
1.65 and 1.5 eV for Si-QD sizes of 2.5, 3, 3.5 and 4 nm 
respectively. The Jsc is found to increase from 
0.3859 mA/cm2 to 1.055 mA/cm2 for 2.5 nm dot size to 
4 nm for barrier layer thickness of 2.5 nm. On the other 
hand, the Jsc also increases with reduction in barrier 
layer thickness, i.e. from 1.055 mA/cm2 for 2.5 nm thick 
barrier layer to 1.247 mA/cm2 for 1.5 thick barrier  
layer. 
 
 
REFERENCES 
 
1. P.S.M. Sze, Physics of Semiconductor Devices, 2nd Ed. 
(John Wiley & Sons Inc.: 2007). 
2. Tae-Wook Kim, Chang-hee Cho, Baek-Hyun Kim, Appl. 
Phys. Lett. 88, 123102 (2006). 
3. V. Vinciguerra, G. Franzo, F. Priolo, F. Iacona, J. Appl. 
Phys. 87, 8165 (2000). 
4. Gavin Conibeer, Ivan Perez-Wurfl, Xiaojing Hao, Dawei Di, 
Dong Lin, Nanoscale Res. Lett. 7, 193 (2012). 
5. Gavin Conibeer, et al., Prog. Photovoltaics: Res. Appl. 19, 
813 (2011). 
6. X.J. Hao A.P. Podhorodecki, Y.S. Shen, G. Zatryb, J. Misiewicz, 
M.A. Greenet, Nanotechnology 20, 485703 (2009). 
7. Kavita Surana, University of Grenoble, France, Thesis 
(2011). 
8. Dawei Di, Heli Xu, Ivan Perez-Wurfl, Martin A. Green, 
Gavin Conibeer, Prog. Photovoltaics: Res. Appl. (2011). 
9. D. Kovalev, H. Polisski, G. Koch, phys. status solidi (b) 
215, 871 (1999). 
10. Nae-Man Park, Chel-Jong Choi, Tae-Yeon Seong, Seong-
Ju Park, Phys. Rev. Lett. 86, 1355 (2001). 
11. Pramila Mahala, Sanjay Kumar Behura, A. Ray, J. Nano- 
Electron. Phys. 3 No1, 979 (2011). 
 
 


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Modeling of Si-QD Solar Cell in MATLAB

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